1 PROJECT SUMMARY/ABSTRACT 2 The ability to image multiple contrast agents simultaneously may greatly benefit the diagnosis of many 3 abdominal and cardiovascular diseases. Promising clinical applications include, but are not limited to, 4 characterization of atherosclerotic plaque composition; differentiation of arterial and venous vasculature; 5 separation of the bowel lumen and wall; and multi-phase imaging in one-single scan. Energy integrating 6 detector (EID)-based dual-energy CT (DECT) enables material-specific imaging and has achieved great 7 success over the past decade, but it cannot perform accurate and stable imaging for multiple contrast agents. 8 Multi-energy CT (MECT) with more than 2 x-ray beam measurements is currently under active 9 investigation, and energy-resolved photon-counting CT (PCCT) has received much attention as an approach to 10 MECT. However, PCCT has 2 major limitations. First, PCCT detectors may produce severely distorted spectral 11 information due to many non-ideal effects, which significantly degrades their performance. Corrections of these 12 non-ideal effects remain promising research topics but have not yet been implemented on a PCCT system 13 capable of clinical imaging. Second, PCCT is associated with very high cost due to lack of mass production 14 techniques. Because of these limitations, the benefit of PCCT over traditional EID-based CT in routine clinical 15 practice has not yet been shown, despite much active research in this area. 16 In this exploratory project, we will test an EID-based approach to MECT for imaging multiple contrast 17 agents. In this approach, a split filter is applied to either 1 or 2 x-ray sources of a dual-source CT such that 3 or 18 4 unique x-ray beam measurements can be made nearly simultaneously. This is a much more cost-effective 19 alternative to PCCT, with potentially comparable or improved MECT performance. The specific aims are: 20 (1) Determine optimal tube energies and beam filters in EID-based MECT by using computer simulations. A 21 whole-body PCCT will also be simulated to compare its performance with the EID-based MECT technique. 22 (2) Implement the EID-based MECT technique on a dual-source scanner, and perform phantom and pilot 23 animal studies. Phantoms with multiple contrast materials will be used to test both the new MECT system and 24 an existing whole-body PCCT scanner. A pilot animal study using pigs will also be performed on both systems 25 to validate the developed EID-based MECT technique in vivo, focusing on two abdominal applications. 26 The innovation of this proposal is that it will be the first to implement an EID-based MECT technique on a 27 clinical scanner, which could readily become an early clinical platform for material-specific imaging of multiple 28 contrast agents. This research is highly significant in that the comparison between EID-based and PCCT- 29 based approaches may redefine the direction of current research toward achieving clinical MECT. The long- 30 term goal of this project is to develop an accurate, reliable and cost-effective approach to imaging multiple 31 contrast agents simultaneously and to investigate various clinical applications of MECT.